Jenkins instance fails to start

Issue

I had disabled the CloudBees assurance Program (CAP) and somehow, after installing a plugin and restarting, my Jenkins instance fails to start.

Explanation

You may have disabled CAP to upgrade a plugin to a newer version that was not yet in CAP. But, after installing it/upgrading it via Jenkins UI (Manage Plugins view) and then restarting, your Jenkins instance failed to start.

This is sometimes caused by a bad dependency, regression in the plugin, or many other possible reasons.

Although we are explaining how to solve it, plase note that is it recommended to have CAP ENABLED at all times, because it helps ensure stability for your plugins.

The recommended way to solve this issue is to stop Jenkins, and restore the backup of the JENKINS_HOME you took before you installed those plugins. If you do not have a backup, please stop Jenkins and take a full backup of the JENKINS_HOME right now (just incase we have to try multiple attempts to fix this issue), once that is complete, we have two possible alternative ways to fix this:

1 - Restoring the affected plugins to the CAP version / deleting crashing plugins
2 - Find the dependencies that are affected by that installation and installing them manually.

Since we enforce at all times to have CAP, we will go thru the first way since it’s, in most of cases, the ideal one.

Environment

Resolution

The ideal resolution here is to have a JENKINS_HOME backup that was created before you had installed the plugin, and restore that backup. The best practice is to take a backup before each update, and if something goes wrong, restore it. If this is not the case, keep reading.

Before continuing; we strongly suggest you to take a backup of your JENKINS_HOME now. There is a risk that manual removal/deactivation of plugins could cause a configuration loss along the way. In a case of configuration loss, doing it this way, you will have a choice to retrieve the configuration.

Go to your JENKINS_HOME/plugins directory, you will see each plugin has a plugin-id.jpi file, and a plugin-id directory. Once you find the bad plugin, delete the plugin-id directory, and either delete the plugin-id.jpi file, or rename it to plugin-id.jpi.bak, and replace it with the correct CAP version. If not in CAP, then use the version of the plugin from before you upgraded it.

Once done, restart Jenkins (Set the url to http://jenkins_home_url:8080/restart in your browser) and proceed. The crashes should be fixed.

Additional Information

If you want to further know about Cloudbees Assurance Program (CAP) you can go here.
[CloudBees-Plugin-Support-Policies]: https://go.cloudbees.com/docs/general/support-policies/plugins

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